1. Field of the Invention
The present invention generally relates to a rotation transmitting mechanism for a steering wheel for use in an automobile. More particularly, it relates to a mechanism for transmitting a rotation of the steering wheel to a rotational member of a coupling device through a cancel cam for a turn signal lever.
2. Description of the Related Art
As well known, the steering wheel is provided with a horn switch, other switches, an air bag and the like which are electrically connected to the terminals arranged in a steering column to connect a power source. It is needless to say that the steering wheel is rotatable, while the steering column is fixed on the body of the automobile. Thus, the connection mechanism for the horn switch and the terminals must include such a coupling device as permitting the rotation of the steering wheel with respect to the steering column.
Conventionally, according to one of the coupling device for accomplishing the above-described requirement, there is provided a flat cable which allows the rotation of the steering wheel. According to another coupling device, there is provided a slip ring arranged on the steering column and a brush arranged on the steering wheel to cooperate with the slip ring.
In any case, the coupling device is, generally, so arranged as to surround a cancel cam which is mechanically coupled with the steering wheel. It is noted that the cancel cam functions as means for returning the turn signal lever to its neutral position when the steering wheel returns to its neutral position.
Conventionally, the rotation of the steering wheel is transmitted to a rotational member of the coupling device by means of the cancel cam. According to a prior art, for example Japanese Laid-Open Utility Model publication 1-89491, the rotational member is provided with a cylindrical lower part having a plurality of projections extending radially inwardly, while the cancel cam includes a sleeve portion having, at its upper circular end, the corresponding U-shaped cutouts for receiving the projections.
Meanwhile, when the steering wheel is assembled to the steering shaft and the steering column is arranged on the body of the automobile, it is unavoidable that the steering wheel and/or the steering column may be not slightly co-axial with the steering shaft due to the dimensional errors and the assembling errors of these members, resulting in the inconvenience of the engagement of the projections of the coupling device and the cancel cam. Namely, the projections may tightly contact the peripheral face of the U-shaped cutouts so that a squeaky noise due to the resulting large friction may be generated when the steering wheel is rotated, or the projections may be accidentally damaged. If the play between the projection and the U-shaped cutout was increased too much in order to avoid the above-mentioned problems, a noise due to the strike of the projections against the peripheral face of the U-shaped cutouts would be generated.